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Frank Kay

Outlook 2016 has begun to assume Exchange 365 and fails to connect to on-premises exchange accounts

Over the past 18 months, I have performed 5 successful SBS2011 to Server 2016 Essentials with on-premises Exchange 2016 for clients of mine, thanks to excellent migration guidance and support from Server-Essentials.  All has been well for months, with clients using various versions of Outlook, ie 2010, 2013, and 2016, and a couple of users with the Office 365 version

I now have several users, using Outlook 2016, on computers both attached to the domain or visiting, or connecting from other locations, where the autoconnect does not work.

Some research on the problem reveals a lot of frustrated attempts to deal with it, and that is has been experienced for some time in various circumstances.  When completing the migrations, we had no such trouble - it has only begun recently, but on 3 separate systems.

Connection of earlier Outlook versions than 2013, and mobile device Outlook apps, and OWA, all continue to work correctly.  OWA provides a workaround, at least.

The failure to connect only produces a 'something went wrong' message.  I have had a protracted 'support' session with Microsoft, which revealed a number of registry keys, and then failed to continue - typically there were hour-long waits for any response, and when I opened Outlook the next time, the promised continuation of the diagnosis did not reconnect.

My clients have not considered moving to Office 365, since they own licensed versions of Office and Exchange, and one of them has a substantial contacts database which is integrated with Exchange via a SQL database.

I post this to ask for advice - if I were to add Exchange 365 Integration to these systems, would this allow accounts established on the on-premises Exchange to continue to work as before, simply by not migrating those accounts?  Or is there anything we can do to resolve the connection problem with the current Outlook clients?

Hoping for some inspiration to replace my frustration!

asked01/26/2020 15:29
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Last Activity 01/28/2020 22:30

1 Answer(s)

  • Mariette Knap

    Hello Frank,

    You may thank Microsoft for this behavior! It started in later versions of Outlook 2016 (16.0.6741.2017 and later versions), it now defaults to O365 even if you have an on-premise Exchange Server. But there is a solution. Please, read this article Unexpected Autodiscover behavior if settings under the \Autodiscover key - Outlook | Microsoft Docs

    You need to set this registry entry:

    Windows Registry Editor Version 5.00

[HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\AutoDiscover]
"ExcludeExplicitO365Endpoint"=dword:00000001

    Save the above to a file called 'ExcludeExplicitO365Endpoint.reg' and import it on a client that has the issue. In rare circumstances you need to create a new Outlook profile

    answered 01/26/2020 16:38
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    Mariette Knap

    Obviously, we want to automate this with a Group Policy created on the Domain Controller. I named the Policy 'ExcludeExplicitO365Endpoint' and linked it to the domain with a WMI filter that limits the scope to Windows clients only. You don't need this setting on any server.

    Frank Kay

    Well, once more I pay homage to the mistress of migrations (and many things Microsoft) - thank you, Mariette!

    I had found the particular article referenced above, and tried it, to no effect - whether it was because Microsoft Support had been playing with my registry settings?  They had introduced a number of registry keys, namely:

    ExcludeScpLookup
    ExcludeHttpsRootDomain
    ExcludeHttpsAutoDiscoverDomain
    PreferLocalXML
    ExcludeHttpRedirect
    ExcludeSrvRecord
    ExcludeLastKnownGoodUrl
    ExcludeExplicitO365Endpoint

    all set to 'Enabled'.  No explanation of what they do.

    If Mariette says something works, it is worth another try, at least - so I removed all these other than the 'ExplicitO365' one, set it to 1, restarted my laptop, and hey presto!  Several happy users, including me!

    Yet another instance of Microsoft driving their vision of computing forward without any thought as to the wide range of stages of advancement in their user base!  They probably would like to have no users at all other than themselves, I sometimes feel.

    replied 01/28/2020 19:10
    Mariette Knap

    Thanks Frank! Have a nice holiday :)

    replied 01/28/2020 22:30
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    replied 01/26/2020 17:16
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